There is a need for low bend loss optical fibers, particularly for optical fibers utilized in so-called “access” and fiber to the premises (FTTx) optical networks. Optical fiber can be deployed in such networks in a manner which induces bend losses in optical signals transmitted through the optical fiber. Some fiber applications that can impose physical demands such as tight bend radii, or compression of optical fiber, etc., that induce fiber bend losses. The requirements that impose these demands include, for example, the deployment of optical fiber in optical drop cable assemblies, distribution cables with Factory Installed Termination Systems (FITS) and slack loops, small bend radius multiports located in cabinets that connect feeder and distribution cables, and jumpers in Network Access Points between distribution and drop cables. It has been difficult in some single mode optical fiber designs to achieve both low bend loss at both large and small bends at the same time.
For example, single mode optical fibers with a low index trench in the cladding are being used for making fibers with low bend loss performance. These fibers have a trench where the depth of the trench is relatively constant across the width of the trench. In these designs, while the performance of the fiber at smaller diameters (˜10 mm mandrel diameter) is excellent (<0.25 dB/turn), the performance at large diameters (˜30 mm mandrel diameter) is not as good as in other bend optimized fibers that have been optimized for larger bend diameters. To improve the bend performance at both small and larger bend radii, fiber designs that include multiple trenches have been proposed. However, such an approach results in additional steps during processing and makes making of the fiber more costly.